- ACHD Policy Manual: Available via Adobe Acrobat pdf files. Please note that the web version of the ACHD Policy Manual is provided as a service and may not reflect.
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- An interval is a duration of time during which the signal indications do not change. For example, a pedestrian phase contains three intervals—Walk, Flashing Don’t.
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State Highway Administration. General Information. The design of improvements on the State highway shall conform to current SHA standards, specifications, and accepted engineering practices. Due to the breadth and complexity of highway engineering practice, a comprehensive treatment of the subject is not possible within this manual.
This Chapter, however, is intended as a starting point and reference on design policies and procedures commonly applicable to access- related improvements. The applicant and/or their professional representative is responsible for compliance with all applicable standards of design practice. In presenting certain requirements, reference is made to the definitions of "routine", "intermediate", and "major" projects, which are found in Chapter 7. Standards and Specifications. Design Standards.
The Federal Highway Administration (FHWA) is an agency within the U.S. Department of Transportation that supports State and local governments in the design.
All designs shall conform to the policies, guidelines, standard practices, and directives issued by SHA and EAPD and the following nationally recognized publications, as applicable: A Policy on Geometric Design of Highways and Streets, American Association of State Highway and Transportation Officials, 2. Manual on Uniform Traffic Control Devices, American Association of State Highway and Transportation Officials, 2.
Roadside Design Guide, American Association of State Highway and Transportation Officials, 1. Other publications, guidelines, standards, and directives recognized and applied by various SHA design offices as may be applicable to the project design. Construction and Materials Specifications.
All construction on the State highway right- of- way shall conform to the latest version of SHA’s Standard Specifications for Construction and Materials, including all applicable Interim Specifications Addenda and Special Provision Inserts. In addition, work shall conform to any approved project- specific provisions. Standard Details. All construction shall conform to the latest version of SHA’s Book of Standards for Highway and Incidental Structures, except where the use of nonstandard or modified designs is expressly noted and detailed on the approved plans. This requirement shall apply regardless of whether the details are included or referenced on the approved plans. Geometric Layout of Improvements. The horizontal and vertical geometric layout for site access improvements and highway infrastructure improvements shall be established in accordance with the following requirements.
Idaho Driver’s Manual August 2015 Published by The Idaho Transportation Department Division of Motor Vehicles P.O. Box 7129 Boise, ID 83707-1129 Phone # (208) 334-8736. TR NEWS 273 MARCH–APRIL 2011 47 sult TCRP Report 100: Transit Capacity and Quality of Service Manual. To assist planners in sizing highway facilities, the. The purpose of this manual is to provide procedures, guidelines, and information concerning highway illumination.
Entrances and Street Connections. The layout of standard entrances and street connections for site and/or subdivision access shall conform to the requirements of Chapter 1. The layout of street connections for collector or arterial routes shall conform to 1. Site Access Improvements. The layout of deceleration lanes, acceleration lanes, bypass lanes, left turn lanes, and other routine site access improvements shall conform to the requirements outlined in Chapter 1. Alternate designs based on accepted engineering practices may be approved on a case by case basis, with appropriate justification and supporting documentation, for use where the standard designs are not feasible.
Highway Infrastructure Improvements. The layout of highway infrastructure improvements shall conform to the requirements outlined in Chapter 1. AASHTO policies referenced in 1. SHA design policy, and accepted engineering practice. Where the intersection includes a County or municipal road, the requirements of the local jurisdiction may also apply at their option.
The geometric layout of site access improvements proposed within the limits of a highway infrastructure improvement shall conform to the requirements of Chapter 1. Highway Alignment. Where a new or modified horizontal and/or vertical alignment is proposed for a State highway, the alignment shall conform to AASHTO policy and pertinent SHA practices.
Developing safe and appropriate alignments for new highways is a complex engineering endeavor which requires proper application of many technical criteria. Excerpts from SHA policy on the design of new alignments are contained in Appendix G. The following Sections outline basic design parameters applicable to alignment modifications that are necessary to accommodate the proposed site access, support new lane allocations, or correct sight distance deficiencies. A change in the horizontal or vertical curvature of the highway centerline and/or through lanes is considered an alignment modification. For purposes of this manual, a tapered lane shift conforming to the MUTCD is not considered an alignment modification.
Design Speed. For geometric design purposes, an operating speed of 1. A lower design speed may be considered but only if supported by an approved speed study that indicates a lower 8. Horizontal Curves. New alignments and horizontal curve modifications shall be designed to provide proper sight distance and handling characteristics for the design speed in accordance with AASHTO policy. The curvature and associated superelevation rates and transitions shall be appropriate for the design speed, route function, and geometric characteristics.
Pertinent SHA design practices for horizontal curves are given in the sections below and in Appendix G. A. Superelevation Rate and Curve Radius. Superelevated Sections are found in curves and on the transitions into and out from curves. Appropriate superelevation shall be provided or maintained for all travel lanes resulting from or affected by the alignment modifications.
The AASHTO design charts shall be used to determine the superelevation to be applied on a particular curve, based on the design speed, curve radius, and maximum superelevation rate (emax) established for the alignment. Maximum superelevation rates for the design of State highways, in accordance with SHA design practices, are given in Table 1.
15. TECHNICAL DESIGN STANDARDS 15.1 General Information. The design of improvements on the State highway shall conform to current SHA standards, specifications, and. Preface Using this Manual i Using this Manual Read this manual if you are planning and/or installing a Data Highway (DH), Data Highway Plus (DH+), Data Highway II (DH.
Use of a consistent emax for the design of successive curves along a route yields predictable handling characteristics and steering efforts as drivers negotiate curves of different radii. For this reason, it is important that retrofitted curve modifications be consistent with the superelevation characteristics of the existing highway. Table 1. 5. 4. 2 Maximum Superelevation Rates.
Application. Maximum Superelevation, emax. New open section facilities. Expressway main lines.
New closed section urban facilities. Interchange loop ramps. District 6. Other interchange ramps. At- grade intersections (signalized or unsignalized)Refer to AASHTO policy. B. Superelevation Transitions.
Superelevated sections shall be gradually introduced, with a uniformly varying cross slope, over an appropriate distance referred to as the transition length. The appropriate transition length shall be determined using the following chart. Application Rate of Change in Pavement Cross Slope per Foot of Transition Length Expressways and urban highways. Other Highways. 0.
Directional Ramps and other two lane ramps. Single lane outer ramp.
Inner loop ramps. Transition Length = Full Superelevation Rate in Curve / Rate of Change in Pavement Cross Slope For simple curves, two- thirds of the superelevation transition length shall be located on the tangents beyond the horizontal curve, while one- third shall be located within the horizontal curve. The use of spiral or compound curves is reserved for select expressways and is not covered in this Manual. Vertical Curves. Vertical curves shall be designed to provide proper sight distance for the design speed in accordance with AASHTO policy, using the pertinent sight distance criteria. For retrofit widening applications, the alignment of the new pavement should match that of the existing highway, unless a safety issue results. Pertinent SHA standards for vertical curve design in Appendix G shall apply.
Profile Grades. Profile grades for new or modified State highways shall be determined in accordance with AASHTO policy. Maximum grades shall be appropriate for the context and function of the State route, addressing the needs of bicycle and pedestrian users as well as motor vehicle traffic. Pavement Cross Slope. Proper pavement cross slope is necessary to provide acceptable vehicle traction, handling characteristics, and pavement drainage along curved highway alignments. The criteria of this Section apply to any widening, reconstruction, or resurfacing of the existing highway associated with or affected by the improvements. A. Widening Along Normal Sections.
On Normal Sections, the existing roadway is crowned at the centerline. Grades for the widening shall be established using the existing or proposed pavement elevations at the edge of the widening and an appropriate cross slope for the new pavement. The cross slope of the new pavement shall be - 2% (- ¼ in/ ft) for widening of existing 2- lane undivided highways, unless otherwise directed by EAPD. The cross slope of the new pavement should be increased to –4% (- ½ in/ ft) for widening of existing multilane undivided or divided highways where more than one existing travel lane is sloped towards the widening.
A typical section shall be provided on the plans and is generally sufficient to illustrate the proposed road grading. B. Widening Along Superelevated Sections. In a fully superelevated section, the entire roadway is banked to slope in one direction. In a superelevation transition section, all or a portion of the roadway is progressively rotated from the normal cross slope to the superelevated cross slope.
For minor widening that will not affect the location of the centerline or travel lanes, the widening should generally be graded to the same cross slope as that of the adjacent travel lane(s), matching the existing superelevation and transition rates. Topographic coverage must be sufficient to accurately define the existing roadway cross slopes across each lane of the existing highway (“spot” elevations taken at the centerline and each lane line). Cross sections at 5. C. Shifted Centerline or Travel Lanes.